Move 'use strict' to file level

Change-Id: I1f0dae4aa168e77c112bcd3688c98b84e4ce5f36
diff --git a/dev/js/src/hint/foundries/mate.js b/dev/js/src/hint/foundries/mate.js
index c7cd2e9..e022664 100644
--- a/dev/js/src/hint/foundries/mate.js
+++ b/dev/js/src/hint/foundries/mate.js
@@ -1,10 +1,12 @@
+"use strict";
+
 define(["hint/foundries","hint/foundries/stts"], function (ah, sttsArray) {
-  var mateSttsArray = sttsArray.slice(0);
+  let mateSttsArray = sttsArray.slice(0);
   mateSttsArray.push(
     ["<root-POS>","<root-POS>","Root Part of Speech"]
   );
 
-  var ah = KorAP.annotationHelper = KorAP.annotationHelper || { "-" : [] };
+  let ah = KorAP.annotationHelper = KorAP.annotationHelper || { "-" : [] };
 
   ah["-"].push(
     ["Mate", "mate/", "Lemma, Morphology, Part-of-Speech"]
diff --git a/dev/js/src/hint/foundries/schreibgebrauch.js b/dev/js/src/hint/foundries/schreibgebrauch.js
index 29eed70..297840a 100644
--- a/dev/js/src/hint/foundries/schreibgebrauch.js
+++ b/dev/js/src/hint/foundries/schreibgebrauch.js
@@ -1,5 +1,5 @@
 define(["hint/foundries","hint/foundries/stts"], function (ah, sttsArray) {
-  var sgbrSttsArray = sttsArray.slice(0);
+  let sgbrSttsArray = sttsArray.slice(0);
 
   // Push specific information for Schreibgebrauch
   sgbrSttsArray.push(
diff --git a/dev/js/src/hint/item.js b/dev/js/src/hint/item.js
index 80ac78b..2fcecee 100644
--- a/dev/js/src/hint/item.js
+++ b/dev/js/src/hint/item.js
@@ -1,6 +1,8 @@
 /**
  * Hint menu item based on MenuItem
  */
+"use strict";
+
 define(['menu/item', 'util'], function (itemClass) {
   return {